1. Field of the Invention
The present invention relates to an image forming method and apparatus and an image forming apparatus, and more particularly to a recording medium conveyance method and apparatus and an image forming apparatus in which cut sheets of recording media are conveyed while being held by attraction on a circumferential surface of a rotating drum or belt.
2. Description of the Related Art
In an inkjet printer recording an image by an inkjet method, the distance from the paper surface to the inkjet head is the distance over which the ink droplets are thrown, which may be referred to as the “throw distance”. From the viewpoint of paper conveyance, a long throw distance is desirable in order to avoid contact between the paper and the inkjet head due to cockling of the paper, or the like. On the other hand, as the throw distance becomes longer, so the landing position displacement of the ink droplets on the paper due to ejection direction defects can become greater, and hence there is a problem in that the image quality falls. Consequently, in order to record an image at high quality, it is necessary to maintain the distance from the surface of the paper to the inkjet head at a prescribed distance or less (e.g., approximately 1 mm or less).
In order to keep the distance from the paper surface to the inkjet head at the prescribed distance or less, it is necessary to hold the paper during conveyance, and this is an indispensable condition in the case of high-speed printing in particular. As conveyance mechanisms for holding and conveying paper, in the related art, there are a method in which paper is conveyed by being held by attraction (e.g., suction, electrostatic attraction, or the like) onto a belt (a so-called belt conveyance method) and a method in which paper is conveyed by being held by attraction (e.g., suction, electrostatic attraction, or the like) onto a drum (a so-called drum conveyance method).
Japanese Patent Application Publication No. 2004-238111 discloses an image forming apparatus conveying paper on a belt, in which the paper is closely fixed onto a surface of the belt and floating up of the paper is prevented, by pressing the paper with a roller while the paper is being held on the belt by electrostatic attraction.
However, if paper is pressed with a roller, then if undulations have occurred in the paper due to cockling, these undulations are pushed toward the trailing end of the paper in terms of the conveyance direction and creases occur in the trailing end portion of the paper in the conveyance direction.